V/F Control - Siemens Sinamics G120P Operating Instructions Manual

Functions
7.5 Motor control
To manually optimize the closed-loop speed controller with the IOP, proceed as follows:
1. Set the ramp-up and ramp-down times of the ramp-function generator p1120 = 0 and
p1121 = 0.
2. Set the pre-control of the closed-loop speed controller p1496 = 0.
3. Enter a setpoint step and observe the associated actual value.
4. Optimize the closed-loop speed controller by changing the closed-loop controller
parameters K
5. Set the ramp-up and ramp-down times of the ramp-function generator p1120 and p1121
back to their original value.
6. Set the pre-control of the closed-loop speed controller p1496 = 100%.
7.5.3

V/f control

V/f control sets the voltage at the motor terminals on the basis of the specified speed
setpoint.
The relationship between the speed setpoint and stator voltage is calculated using
characteristic curves. The required output frequency is calculated on the basis of the speed
setpoint and the number of pole pairs of the motor (f = n * number of pole pairs / 60, in
particular: f
The inverter provides the two most important characteristics (linear and square-law).
V/f control is not a high-precision method of controling the speed of the motor. The speed
setpoint and the speed of the motor shaft are always slightly different. The deviation
depends on the motor load.
If the connected motor is loaded with the rated torque, the motor speed is below the speed
setpoint by the amount of the rated motor slip. If the load is driving the motor (i.e. the motor
is operating as a generator), the motor speed is above the speed setpoint.
The V/f control can also be used in the test mode.
Parameter p1300 sets the characteristic curve.
360
and T until the drive runs optimally.
P N
= p1082 * number of pole pairs / 60).
max
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A